Shrink Fit: The High Accuracy Toolholder of Choice(2)

6. Reduction of toolchanging time/less toolholder accessory inventory
Nothing beats the tool change time of shrink fit chucks if the process is joined with a capable inductive shrink fit machine. Tool changes can be done in five to 10 seconds, and most importantly, consistently. This allows the toolholder assembly to be in the machine making chips more of the time, than out of the machine waiting to be changed. Also, a shop needs very little additional toolholder accessory inventory (i.e., collets, nuts, seal disks, etc.). This simplifies the process.

7. Cleanliness of setup
A shrink fit chuck typically is a sealed system by design. Therefore, the introduction of contaminants in the bore are minimized (such as graphite dust or chips). If contaminants are introduced to the bore of a toolholder, oftentimes run-out accuracy is compromised.

8. Coolant options
Shrink fit chucks often have clever methods to deliver coolant or air/oil mist down to the cutting edge of the cutting tool. This helps with the proper removal of chips and can also aid in providing better finishes. In addition, if a mold shop does high precision drilling, a shrink chuck makes an excellent holder for coolant through drills since no accessories or special collets are needed—the sealed design of the toolholder simply allows the coolant to flow through the cutting tool.

Threaded holes for fine balancing and cool-jet ports shown to deliver coolant to the nose of the cutting tool.

9. Consistency of setup
Shrink fit holders provide the best repeatability from toolholder setup to toolholder setup. This is especially beneficial for those shops running lights out. For example, all toolholder setup operators set the toolholders the same with shrink fit holders. There are no variables—such as over-tightening or under-tightening a collet nut or not cleaning out a chuck sufficiently. Also, as mentioned the balance characteristics are the most repeatable. This combination of consistency allows a shop to truly monitor their tool life and understand how many parts they can machine with each toolholder setup—again, this is truly an important part of getting to the point of lights out machining.

10. Availability of shrink chucks
Most of the major toolholder builders in the world now offer shrink fit chucks as a standard. Therefore, mold shops are not roped into proprietary high precision collets or press fit systems that sometimes are only available from one manufacturer.

Selection of the Proper Shrink Fit Chuck
While there are many suppliers of shrink fit chucks available, there are good and bad shrink fit chucks available. It is important to do research related to the selection of a toolholder for your particular application.

Typically, the initial purchase of your toolholders will last the life of your machine tool. Studies have found that the overall expense of toolholders equals less than 0.5 percent of the overall machining process during the life of the machine tool.

Shrink extension assembly provides ability for deep reach and clearances.

The relationship between the bore of the holder and the taper lead to the accuracy of the chuck. It is important to choose a company that truly makes their own product and specializes only in the production of toolholders. This guarantees you the most consistent and accurate toolholder available for your job.

The material of the shrink fit chucks is also a key element in making the correct selection. If a substandard material is used, one might shorten the life of the shrink fit chuck based on limited heating cycles. A shrink fit toolholder made of the correct material should remain effective indefinitely.

Also, it is important that the chucks subscribe to the DIN standards on the nose dimensions so that all cooling options from the shrink fit machine side can be utilized.

Collet chucks and shrink fit chucks.

In general, it is recommended to purchase chucks with many “options” built-in (such as balanced so that there is under 1 gmm of unbalance in the chuck, balanceable design, bore for the data chip, form “DIN B” coolant delivery option, etc.) so that you are not limited in the future as your operation evolves.

Finally, the company making the chucks should be an industry leader, constantly putting further efforts into research and development into new toolholding concepts that can further strengthen the role of shrink fit toolholders in the mold market.
For example, the recent development of a shrink fit chuck1 that provides an anti-vibration feature in a shrink chuck. This feature helps dampen the vibration during roughing operations that had at one time occurred with standard shrink fit chucks due to the extreme rigidity of the setup.

Summary
It is often stated by shop owners and plant managers that shrink fit tooling has been the best investment they have made in the past five years. Acceptance of the use of shrinking technology in the mold and die market has played a vital role in strengthening North American manufacturing capabilities and preparing it for continued growth.

References
1 Haimer’s Power Shrink fit chuck.

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